1. Field of the Invention
The present invention relates to a disk-type recording medium drive for driving a disk-type recording medium such as a magnetooptical disk and a method of self-diagnosing such a disk-type recording medium drive.
2. Description of the Prior Art
Conventional apparatus for driving disk-type recording mediums such as magnetooptical disk drives carry out a self-diagnosis when a magnetooptical disk is loaded. In the self-diagnosis, the magnetooptical disk drive automatically writes test data in a test area radially inward of a recording surface on the magnetooptical disk, reads the written test data, and compares the read test data with the test data to determine whether the recording and reproducing system including an optical pickup, etc. is operating normally.
The above self-diagnosis process will be described in specific detail below. Desired data are recorded on and read from a magnetooptical disk sector by sector by a magnetooptical disk drive. In the magnetooptical disk drive, one sector on the magnetooptical disk is composed of 512 bytes.
The test data are determined in advance by a program executed by a microprocessor unit (MPU) of the magnetooptical disk drive. Specifically, the test data are 512 bytes or a sector of data comprising two repeated sets of 256 bytes of data 00h, 01h, . . . , FFh.
The test data are written in the test area of the magnetooptical disk which is capable of recording one sector of data.
The magnetooptical disk drive can rewrite data that are written in the magnetooptical disk by erasing the written data and then writing new data on the magnetooptical disk. More specifically, to erase the written data from an area of the magnetooptical disk, a magnetic field is applied in one direction to the magnetooptical disk, and a data erasing laser beam of strong laser power is also applied to the area of the magnetooptical disk. The area of the magnetooptical disk is now magnetized in one direction, thus erasing any written data from the area. Thereafter, the applied magnetic field is reversed, and a data writing laser beam of strong laser power is applied to the area of the magnetooptical disk. The written data can be read from the magnetooptical disk by accessing the magnetooptical disk with a laser beam of weak laser power.
Therefore, for recording test data in the test area, it is necessary to erase the test data which have previously been written and then write the new test data in the test area.
The conventional magnetooptical disk drive uses the same test data in every cycle of the self-diagnosis. Consequently, even if the laser power applied for erasing and writing the test data is too low to erase the previous test data and write the present test data due to a failure of the recording and reproducing system, the magnetooptical disk drive may read the test data which have previously been written in the test area, and may determine that the recording and reproducing system is operating normally.